1. Field of the Invention
The present invention relates to a download terminal and a content utilization system for copying and bringing out an encrypted content with managed viewing time limit from a download terminal to an exchangeable medium to reproduce the encrypted content by a reproducer.
2. Related Art of the Invention
In recent years, owing to the development of the Internet, techniques for downloading and reproducing movies, music, and the like are generally used. A large number of services are provided for downloading, through networks, contents from servers, which perform content delivery of movies, music, and the like, to PCs, AV apparatuses, cellular phones, and portable apparatuses.
In such content delivery services, there are content sales of a sell-off type with which a user can permanently view purchased content and rental sales with which a user can view downloaded content until a limited viewing time limit.
In typical content sales of a download type, a content provider that supplies content operates a content server and a DRM server. A content receiver on a viewer side downloads an encrypted rental content from the content server and acquires, from the DRM server, a decryption key of the encrypted content and viewing conditions for the content. The viewing conditions for the content include information concerning a viewing time limit within which a user is permitted to view the content and a copy condition for the content.
When the content receiver reproduces the rental content, the content receiver refers to a viewing time limit designated from the DRM server. If the viewing time limit is not exceeded, the content receiver starts the reproduction of the content. If the viewing time limit is exceeded, the content receiver carries out deletion of the content. In some cases, the content receiver writes out a rental content to an exchangeable medium such as an SD card together with the viewing time limit. In this case, when a reproduction terminal for the SD card starts to reproduce a rental content or has ended the reproduction of the content, the reproduction terminal checks the viewing time limit for the content, and deletes the content if the viewing time limit is exceeded. As a method of reproducing content with viewing time limit of this type, for example, there is a method described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-227282).
FIG. 28 is a sequence diagram for a terminal that downloads a content from a server and moves the content so that the content is viewed in another terminal in conventional content downloading as described in Patent Document 1.
A download terminal 601 can view a content by storing the content distributed from a server 600 and acquiring a viewing license of the content from the server 600.
To allow the content to be viewed in another viewing terminal 602, the content can be moved from the download terminal 601 to the viewing terminal 602. However, the server 600 manages the viewing license in association with the download terminal 601. Therefore, the viewing terminal 602, which is another terminal, acquires a viewing license by itself from the server 600 to view the content.
Regarding the forms of the viewing license to be provided, there are (i) a viewing license with viewing time limit for providing a reproduction permission condition of the target content by designating absolute date and time, and (ii) a viewing license with viewing term such that absolute date and time is not designated when the license is provided and only a viewable period, such as 48 hours, is designated for determining the viewing time limit upon the first viewing on the terminal.
If the content is provided with the viewing license with viewing term, the terminal that reproduces the content does not acquire the viewing license from the server 600 again. The terminal itself determines and sets, for example, the date and time after 48 hours from the start of the initial reproduction of the content as the viewing time limit of the content.
Also, regarding the forms of selling a rental content, there is what is called pack selling. The pack selling provides, for example, all twelve episodes of a TV drama as one content group, or as a package, where the twelve episodes are provided at a lower price than the episodes to be individually purchased. In this case, the price for the service paid by the user to the service provider is lower. But the viewing time limits of all the pack contents are usually unified. Specifically, the viewing time limits of all twelve contents are set to the same date and time when viewing of any one of the contents is started after the download of the twelve contents.
However, in the above conventional technique, there is a problem that the viewing time limits of the pack contents cannot be unified when the rental content is written out, without a determined viewing time limit (rental content provided with viewing license with viewing term), to an exchangeable medium such as an SD card to be viewed by the portable terminal and the like.
This problem will be described below.
For example, when a download terminal writes out some of the rental contents sold in pack to an exchangeable medium such as an SD card to view the content in a portable terminal or the like, the viewing time limits need to be synchronous with the contents left (not written out) in the download terminal.
If one of the rental contents sold in pack is already viewed on the download terminal, the viewing time limit of the pack is determined. Therefore, a synchronization state can be secured if the viewing time limit is inherited when a content is written out to an exchangeable medium. On the other hand, if some of the rental contents in the pack are written out to the exchangeable medium when none of the rental contents in the pack are viewed, the rental contents that need to share the viewing time limit are to be saved in storage media physically separated from each other. Therefore, the viewing time limits are to be separately set at initial view, and the viewing time limits cannot be synchronized.
FIG. 29 is a sequence diagram, in which the download terminal 601 that has received pack rental contents from the server 600 writes out some of the contents of the pack to an SD card 606, and the viewing terminal 602 starts to view the content on the SD card 606.
An HDD 605 of the server 600 stores twelve contents with content numbers C1 to C12 in a pack. A case will be considered in which the download terminal 601 downloads nine contents with content numbers C1 to C9 of the twelve contents and writes out (moves) five contents with content numbers C1 to C5 to the SD card 606.
If none of the contents with content numbers C1 to C9 have been viewed in the download terminal 601 before the contents are written out to the SD card 606, the viewing time limits of all contents with content numbers C1 to C12 are not determined yet and, for example, a viewing term is only designated e.g., the contents can be viewed during 48 hours from the first viewing.
When any of the contents with content numbers C6 to C9, which are left in the download terminal 601, is viewed at the download terminal 601, the viewing time limits of all contents with content numbers C1 to C12 need to be determined so as to be synchronous with the content. However, the contents with content numbers C1 to C5 brought out by the SD card 606 are under the management of the viewing terminal 602, and the download terminal 601 has no means to determine the viewing time limits of the contents with content numbers C1 to C5. The download terminal 601 also has no means to determine the viewing time limits of the contents with content numbers C10 to C12 that are not yet downloaded to the download terminal 601. There are such problems in the conventional technique.
The problem occurs not only for pack contents but also for a content when the content is copied and written out to an exchangeable medium, such as the SD card 606, while the original content is left in the download terminal 601. More specifically, if a copy of a content without a determined viewing time limit is written out to the SD card 606, the viewing time limit of the content left in the download terminal 601 is determined when the content is reproduced by the download terminal 601, but the viewing time limit of the content written out to the SD card 606 is determined when the content is reproduced by the viewing terminal 602. Therefore, different viewing time limits are set for one content.
In consideration of the above-described conventional problems, an object of the present invention is to provide a download terminal and a content utilization system capable of synchronizing viewing time limits of a plurality of contents that need to have the same viewing time limits even if some of the contents, the viewing time limits of which are not determined yet, among the plurality of contents are written out to an exchangeable medium before the viewing time limits are determined.